The requirements for clean air have forced engineers and building owners to improve the quality of air filtration devices used in office buildings and sophisticated “zero” tolerance clean rooms. In many buildings, air filtration devices comprise a series of filters placed upstream of the HVAC system. The filters are used to remove the contaminants in the air flowing through the HVAC system.
Typically, the filters are placed within a filter bank assembly having frames for holding each respective filter. The frames are fastened together to form an array of frames that retain the needed filters. Each frame is sized slightly larger than the filter placed therein, and is formed with a sealing flange which extends around the inner circumference of the frame. When a filter is inserted into a respective frame, the sealing flange abuts the filter. A gasket or other type of sealing device may be placed between the filter and the sealing flange in order to provide a better seal.
The filter is retained within a respective frame with a spring clip or other type of retention device. The spring clip tensions the filter against the sealing flange of the frame. If a pre-filter is used, then a second spring clip is used to mount the pre-filter to the filter and the frame.
Numerous problems develop with the type of filter retaining assembly described above. Specifically, air can leak downstream in the gaps between individual frame members and also between the filter and the frame. The spring clips that are used to fasten the filters to the frame can become unfastened to the frame when the filter is not in place and can become lost. Furthermore, the spring clips cannot hold the pre-filter in place when air is not flowing.
Another problem occurs when multiple frames are stacked together to form an array of filters. The array of frames will flex due to their lack of rigidity. The flexure of the frames will cause gaps between the frames and the filters, and adjacent frames thereby leaking contaminants into the airstream.
The present invention addresses the above-mentioned deficiencies in air filter retaining systems by providing a plurality of frames that prevent air leakage. Specifically, the air filter restraining system of the present invention provides a plurality of interlocking frames connected together to retain multiple filter elements. The frames interlock and seal together to prevent contaminants entering the downstream flow. Furthermore, the frames can be strengthened with a vertical member to provide better rigidity than the prior art systems. The frames of the present invention also include a better method of sealing the filter to the frame.